Generally, a vehicle suspension system is provided between a chassis and an axle for absorbing vibrations or impacts generated during traveling of a vehicle while supporting the weight of the vehicle and relieving vibrations or impacts transmitted to the vehicle and a driver, thereby improving ride comfort and securing driving stability of the vehicle.
Typically, the structure of the vehicle suspension system is configured such that an upper seat and a lower seat are installed in a shock absorber to be spaced apart from each other, a coil spring is provided between the upper seat and the lower seat installed in the shock absorber, and a coil spring pad is provided between the coil spring and the lower seat.
The shock absorber includes a cylinder and a piston rod, and a piston valve or the like is provided in the piston rod positioned inside the cylinder.
The coil spring is intended to attenuate vibrations and impacts along with the shock absorber, and is made by winding a thick steel wire in a spiral form. When an external force is applied to compress the shock absorber, the coil spring is compressed as well, and then the coil spring is restored by an elastic force.
An upper seat and a lower seat are provided at the upper and lower portions of the coil spring to receive and support the coil spring.
The lower seat is usually fixed to the outer circumferential surface of a cylinder of the shock absorber, and the upper seat is coupled to an end of the piston rod.
The coil spring pad is provided between the coil spring and the lower seat to prevent direct contact between the coil spring and the lower seat and to absorb and mitigate an impact generated between the coil spring and the lower seat, thereby preventing the lower seat from being damaged due to the operation of the coil spring.
Meanwhile, when a vehicle is running, the coil spring provided in the suspension system repeats compression and extension depending on the road surface condition, and this operation of the coil spring generates a clearance between the coil spring and the coil spring pad.
Further, in the state in which the clearance is generated, the repeated operation of the coil spring in the vertical direction causes the coil spring pad to be torn.
Therefore, Korean Patent Laid-Open Publication No. 10-2013-0135492 has proposed an improved lower spring structure. However, since the contact area between the coil spring and the coil spring pad is not big in the above spring structure, stress is concentrated on an accommodating groove of the coil spring pad. Thus, when the compression and extension of the spring are repeated, the pad may be permanently deformed in the vertical direction, which may cause tearing of the pad.
In addition, in the above spring structure, since the coil spring pad cannot cover the entire area of the lower seat, except for through-holes thereof, there is a problem in which dust collects on the lower seat as the vehicle travels and dust is not easily discharged through the through-holes.
In addition, Korean Patent Publication No. 10-1579924 has provided a spring pad for a suspension spring for preventing foreign substances from accumulating on the upper surface of the spring pad.
However, it is different for the above spring pad for a suspension spring to prevent the pad of the coil spring from being permanently deformed in the horizontal direction by a compression force repeatedly applied to the operating coil spring in the vertical direction.
Furthermore, when the compression and extension of the coil spring are repeated with respect to the spring pad for a suspension spring, the coil spring pad may be pushed outward to be thus permanently deformed in its shape.